How the Universe Works: The Life of Stars

Despite what many say, space is neither dark nor it it empty; in fact, it is positively teeming with life, giant stars forming and dying, black holes swallowing up great suns and planets, asteroids colliding and smashing together to form massive belts expanding throughout a solar system. Space itself almost seems alive, living on a scale that it much longer than ours. But one element stands apart, one element allows all of this life to happen, and these elements are tiny points of light you see, swirling millions of light-years away.

A star begins its life as a cloud of gas called a nebula, where clumps of matter will coalesce until a sufficient mass has been reached, and gravity begins to pull more gas and dust into this point. The star will slowly gain mass and begin to heat up, the core of this cloud forming what is known as a ‘protostar’. The protostar continues to heat up until nuclear fusion can take place, the process by which two atomic nuclei combine to form a heavier atom, and how stars produce their immense energy. The remainder of gas and dust surrounding the young star will form planets and begin a steady orbit, and a solar system has been born.

A star about the size of the Sun lives approximately 50 million years. A star will ‘die’ when nuclear fusion has reached the heaviest atom it can produce, iron, after which energy is consumed rather than released. At this point, most stars will begin ejecting their outer layers, some continuing to do so until the immensely hot core of the star is exposed, called a ‘white dwarf’. This dwarf is supported only by the pressure caused by fast-moving electrons, and will eventually fade away as it slowly cools. This is the fate of most stars smaller than 1.4 times the mass of our Sun.

Sometimes, a white dwarf’s immense mass (and consequently gravity) will pull matter from another nearby body, usually hydrogen from a nearby star (in a binary star system). When it has enough hydrogen, nuclear fusion will again take place, a burst of light ejecting from the dying star. This process will then repeat, forming a nova. If the star accumulates enough matter, it will collapse in on itself and explode in what is known as a supernova.

A star with great mass will die in a supernova when it has reached the ‘iron peak.’ It will be unable to support its own mass and collapse inward in a matter of seconds, the outer layers bouncing off the inner and is expelled outward with a great amount of force. If a star with about 1.4-3 solar masses dies in a supernova, the collapse will result in the combination of electrons and protons to form neutrons, and consequently a neutron star. These stars have immensely powerful magnetic fields that often “accelerate atomic particles around its magnetic poles producing powerful beams of radiation”(NASA). As the star rotates, these beams may be aimed toward Earth, where we can record them and identify the neutron star as a pulsar.

Sometimes, a star will collapse into a black hole, “an infinitely dense object whose gravity is so strong that nothing can escape its immediate proximity, not even light”(NASA).